RV Sonnenkreis - Decoding Universal Cartographics

[drkaii]

Does anyone fully understand this? If so could they please send me a private message so we can have a chat about it on skype? I want to make another exploration video and include this as part of it, but I have some questions. I've asked Jackie himself too but he no respond fast enough and me is impatient

 

[Ziljan]

estimated luminosity based on the mass (M ** 3.9, was trying a variety of powers to see what fitted).

(This highlights the need for basic peer review to catch my blunders. I've been wondering about starting a Journal of Frontier Astrophysics, or something similar but with a snazzier title. )

I think what we're looking at from the Stellar Forge are several distinct types of star system - the various curves on the HR diagram - each of which obeys a standard relationship or set of relationships, but not as complicated as the real-world ... whether that is the start point the game uses for calculating mass and radius or whether the mass and radius are calculated using formulae which happen to produce that result I don't know.

(I suppose the world of 3302 would be great for studying (at least short-term) stellar evolution, as you could watch the last few tens of thousands years of history for every star in as much detail as you liked.)

Look forward to working with you.

3.9 is probably a good estimate for the most common mass of main sequence stars in the game: 0.4 - 2 solar masses. But if you want to make a more accurate HR diagram at the temperature extremes of the MS, I suggest you try the derived mass-luminosity relations in my post above for dwarfs and more massive stars. Since they never directly state the luminosity, I think it's safe to assume that it isn't necessarily a part of the stellar forge calculation. But you are absolutely right, we could check both high mass and low mass MS stars to see which mass-luminosity power ratio they follow, the approximate ~T^6 or the more accurate linear ~M (for very high mass) and ~M^2.3 for low mass stars.

Also since your temps range isn't logorithmic, you are missing the nice characteristic gentle S shape on your HR diagram that will allow us to more easily see the true nature of the mass-luminosity at low temperature stars, as well as as other medium-mass variations and evolutions. The number of high temperature stars you have logged is very impressive. Though, if you are looking for stars on the asymptotic giant branch, you may want to focus on (ie logarithmically spread out) the regime below 10,000K. One area that I would like to take a closer look are proto stars on the Hayashi or Henley tracks. I have only done a cursory look at the temps to see if they were in the ballpark, but haven't done a isochronic luminosity survey to see if their T-L evolution is accounted for.

I am extremely impressed by your methodology btw. "Blown away" would be a more precise term. . And I would be privileged to help you in this quest to crack the stellar forge code. My biggest hope is that we can find a way to predict stars with high metallicity. But really we can only measure this indirectly from He Giants and metal % of HMCP and MR planets. I wish that Frontier had included Z or even better, Fe/H in the galaxy map. Finding a corollary to this info in the naming scheme would be game changing for explorers. Beyond that, we may just have to try to see if there is a moderate correlation between metallicity and galactic radius /altitude / proximity to neutrons/spiral arms.





@Kaii, pls verify with CMDR Silver, but I am pretty sure this project is still pretty deep in the developmental stage. Just to be clear are you referring to the naming scheme meanings? the physical properties of the stars themselves? or both?

 

[Andrew Gaspurr]

Does anyone fully understand this? If so could they please send me a private message so we can have a chat about it on skype? I want to make another exploration video and include this as part of it, but I have some questions. I've asked Jackie himself too but he no respond fast enough and me is impatient

I think it has got something to do with procedural nomenclature matching the Hertzsprung-Russel diagram, i.e. do the spectral classes that seem to reflect a star system's letter and number code also fit into the H-R system? Or something like that?

Edit: Also, I wished FDev would include a star's metallicity statistics, but then again, since they would obviously be generated procedurally, it's questionable if they would be helpful anyway.

 

[Vitamin Arrr]

I think it has got something to do with procedural nomenclature matching the Hertzsprung-Russel diagram, i.e. do the spectral classes that seem to reflect a star system's letter and number code also fit into the H-R system? Or something like that?

Edit: Also, I wished FDev would include a star's metallicity statistics, but then again, since they would obviously be generated procedurally, it's questionable if they would be helpful anyway.

Yes, it does correlate with H-R generally.

The A-G types in the naming convention are a byproduct of Stellar Forge's method of ensuring the proper ratio of star types (lots of Ms and Ks, some Gs and Fs, few As and higher).

They divide the galaxy into seven overlapping boxel grids where each grid is half the resolution of the previous grid. It is a technique similar (in an abstract, structural sense) to the approach in 3D graphics of using stacked levels of detail for performance optimization (http://en.m.wikipedia.org/wiki/Level_of_detail)—except, here, rather than optimizing performance with levels as less complex polygons and only instantiating one level of detail at a time, they instantiate each level simultaneously as ovelapping boxel grids to ensure the occurence density of the types of children of each cell match what we'd expect to find based on H-R.

Of course depending on where you are in the galaxy, what Jackie has found (and I've seen too) is that the types represented by the names, the precise arrangement of boxels, and the shape of the sector (border placement) varies by sector. There are hidden parameters we're not privvy to, but which we can try to guess at, that determine the deviations from what I might call the "abstract sector grid class" (to use an object-oriented programming term; not sure if FD actually uses OO for this however!).

 

[Andrew Gaspurr]

Wow, thanks for the heads-up. You ever learn in this forum.

How are those procedurally generated layers influenced or altered, when you have an actual astronomical object put into a procedural sector, like NGCs, 'Col' (Collinder catalogue) or 'Tr' (Trumpler object) appearing in e.g. PNOE HYPAI or WENGOEO. Do they constitute another instanced layer that just simply adds known data? I am thinking of a system that for example is calles NGC 6530 Sector DG-A e1-13. It has both properties of a procedural and a factual system placement, no?

 

[Ziljan]

I think it has got something to do with procedural nomenclature matching the Hertzsprung-Russel diagram, i.e. do the spectral classes that seem to reflect a star system's letter and number code also fit into the H-R system? Or something like that?

Edit: Also, I wished FDev would include a star's metallicity statistics, but then again, since they would obviously be generated procedurally, it's questionable if they would be helpful anyway.

Yes, it does correlate with H-R generally.

The A-G types in the naming convention are a byproduct of Stellar Forge's method of ensuring the proper ratio of star types (lots of Ms and Ks, some Gs and Fs, few As and higher).

I think there is some confusion here about what an HR diagram shows, and about what the stellar classifications mean.

The HR diagram relation shows the temperature (or color) vs the total luminosity (or energy output). Stars can have the same color-temperature (eg the same letter OBAFGKM) and yet have very different radii and thus very different energy outputs. Likewise stars can have the same mass and yet be at very different parts of their evolution and thus have very different color-temperatures, different radii and thus very different energy outputs.

For example: Aldeberan may have begun its life as a AV or FV star, but is currently a KIII red giant star of ~1.5 solar masses and a radius of ~44 solar radii. Whereas 70 Ophiuchi is a 0.9 solar mass KV with a 0.9 solar radius main sequence star. Two very different stars with the same temperature and color, hence both class K. Yet not remotely the same in terms of energy output, lifespan, or what kind of planets/materials you'd expect to find around them.

The letters A-H have been shown to relate the mass of the star, but not necessarily the temperature-color. There may be a case for this some where in the naming scheme, but it hasn't been proven yet.



As for knowing the metallicity. It would be quite useful imo. Granted it is no guarantee of success of finding specific planet/material types. But we explorers are gamblers who play the odds and like to twist them in our favor whenever possible. Many explorers already mostly look at FKG stars for Earthlikes and terraformables, even though the odds of finding them are still fairly low even within this subset, and still possible outside of it. If you could tell from looking at a system in the gal map that a system was low metallicity, then you would know that they have an even lower chance of having ELW or TF candidates, and you could filter the map appropriately. If you could tell which systems had high metallicity, then this could increase your chances of finding planets rich with better quality material nodes.

That is the whole reason I have been looking at young systems for materials because they have a higher chance of being more metallic. It appears to be a weak correlation and this is similar to the reason that ELW are only weakly correlated with G systems, because there are no guarantees, only better odds. Still, they are good places to look if you're filtering.

 

[Jackie Silver]

Thanks again to everyone for your contributions - I've corresponded with Dr. Kaii and we worked out the confusion - Vitamin Arr that's interesting stuff with the sector shapes! I wonder how they have decided on the shapes and what makes things move out of their correct positions.

I'm a bit frazzled at the moment so I'm just honking at stars for a bit - I've collected some more data on bright giant stars and I'm collecting data on B subgiants and giants at the moment. GREAE PHIO and BOEFT are very fruitful grounds for looking. I've been keeping an eye open for cooler subgiants but haven't seen any - I finished my third survey of landable worlds earlier and there weren't any in there, I must have looked at a couple of hundred systems over the course of the landable worlds surveys and don't think I've had any dim subgiants so far. It is possible that I've been missing subgiants because they're not distinctive on the map, but for the landable worlds surveys I'm exhaustively scanning everything in an area so they should show up. Of course they should be quite rare, so maybe just a question of time.

I will upload the latest log file tomorrow - we may be able to get somewhere with the mass / radius / temperature / age relationship by looking at the K Orange Giant stars because they're all in such a small range of values that some of the masses and radii are equal between systems where the temperature and age are different. Quite hopeful for that.

I love this game.

 

[Andrew Gaspurr]

I think there is some confusion here about what an HR diagram shows, and about what the stellar classifications mean. (...)

Yes, I seem to have mixed that up a bit. Still, fascinating that FDev implemented a system that seems to work with actual mass/luminosity data and not just 'invents' stars on the fly. What has always puzzled me though, is the question if the spectral classes of stars are a one way street that stars go when they get older, i.e. will all A stars become F -> G -> K -> M and then go red giant? I think not?

As concerns metallicity, I had in mind using this to discern if a given 'neighbourhood' of stars or a star cluster formed out of the same cloud. When I headed out into procedural space I often found tight groups of B0 VZ stars and wondered if that ment that they should be associated. If you now had their metallicity available you could draw your conclusions, since you cannot analyze their spectral absorption lines, since it is internet pixels you see (obviously).

This metallicity value would of course just provide immersive or 'fictional' astronomical data, but hey, we never run out of creative ideas to take ingame data and make up our own SIMBAD with it, no?

Edit: I love this game, too. And this forum...

 

[Vitamin Arrr]

The letters A-H have been shown to relate the mass of the star, but not necessarily the temperature-color. There may be a case for this some where in the naming scheme, but it hasn't been proven yet.

I just said there was a correlation... not a direct link. I'm not confused about what H-R means. Anyways... just sayin'! I appreciate your pointing that out tho.

 

[Vitamin Arrr]

Also... all I can say is that where the script predicts D sector boundaries to exist is incorrect in NGC 1664. But it seems to get C correct usually. If there is some randomness thrown into this, it would explain a lot, but it may be that the "cornerstone" of D naming (where rows restart) snaps to the next grid down, rather than the grid that the naming got its cornerstone from. In otherwords, namespace and coordinate space (XYZ) may not be aligned in a way that a direct relationship between D and A on both counts would suggest. It may be rather that D's namespace is anchored to A but its coordinate space is anchored to C, the next grid size down... so that AV-Y D#'s anchor corner snaps to WJ-Z C#'s anchor corner.

This would help explain why you sometimes see D stars from different sectors (like at the border of SLEGI and SLEGAO) where they seem to be invading each others' space. If I'm right, then there should be fairly wide gaps with no B stars around the borders of sectors... or at least around the southern and northern borders. I'll check next time I'm on.

Another anomalous weirdness about NGC 1664 is that its lowest sub-sectors have only one, or just a small handful, of randomly numbered stars. Example: TY-S C3-7 is the only star in TY-S C3. There is no -6 or -5, etc. ... at least, not that comes up in search. Could just be a search bug? Will check manually later.

BTW, I have converted the decoder script to Swift and may post an iOS and a Mac app of it later.

It could also be that we are in seven galaxies, which coincide spaciotemporally, but with certain mild offsets...

 

[Ziljan]

Yes, I seem to have mixed that up a bit. Still, fascinating that FDev implemented a system that seems to work with actual mass/luminosity data and not just 'invents' stars on the fly.

Yes it is very fascinating, and why I love this game.

What has always puzzled me though, is the question if the spectral classes of stars are a one way street that stars go when they get older, i.e. will all A stars become F -> G -> K -> M and then go red giant? I think not?.

Technically yes, but the transition is so quick that if you blink you might miss it.

If you want to see how quickly they transition, check out the link below and use the slider to age the star prematurely.

Notice how at 1 GY, a 2 solar mass A star is still within the A range of temperature-color >7300 K. And then at 1.14 GY it becomes an F IV subgiant burning He in the core. Almost immediately at 1.15 GY it transitions to the asymptotic giant branch as a KIII. So yes somewhere in there it was also a GIV subgiant, but it's such a short time frame that it's pretty unlikely that you will find it on the gal map.

http://astro.unl.edu/naap/habitablezones/animations/stellarHabitableZone.html

This should also answer Jackie Silver's earlier question about why it was so hard to find lower mass class IV subgiants.

Perhaps we can look at relatively low temperature proc-gen subgiants (i.e. stars which should be moving away from the main sequence up the red giant branch) as they seem to be almost entirely absent, if we can find some it might throw some light on what is going on?

The IV subgiant phase is relatively brief in all stars, but for cooler (ie lower ZAMS mass) IV subgiants you need to wait a very long time. In the case of the Sun you'll have to wait ~10 billion years for He burning to kick in. The universe is only ~13.8 GY old! So of course the only IV giants out there are going to be bright massive stars that age very quickly and have had time to move off the main sequence. Likewise with the less rare class III giants.

As concerns metallicity, I had in mind using this to discern if a given 'neighbourhood' of stars or a star cluster formed out of the same cloud. When I headed out into procedural space I often found tight groups of B0 VZ stars and wondered if that ment that they should be associated.

That is darn clever of you, sir. Yes sibling stars in an HII region should have the same age and metallicity since they formed at the roughly the same moment in galactic time and from the same molecular clouds.

 

[Jackie Silver]

I said I'd upload the latest log file today but I merged a couple of other survey files into it and then was distracted by a host of stars of unusual types and then found I just had to start a fourth survey of landable worlds.

Spoiler

I love the total absence of smell from remote balls of fusing hydrogen in the eternal night.

In the meantime, here's a mass vs age plot of stars, highlighting evolved stars and stellar remnants.

The new data I'm gathering includes more M giants, carbon stars and stellar remnants, so should hopefully improve the coverage, but you can see that there are major gaps for B stars at the high and low ends of mass. In principle we should be getting neutron stars from B stars over about 8 solar masses and black holes from O stars over 25 solar masses. By playing with the fraction of the parent star's mass that the solar remnants have, the various stellar remnants can be more or less shunted into their proper places (as I've done on the plot) but that's highly speculative, and in any case the masses for stellar remnants in Elite are very peculiar and Just Plain Wrong in some cases like neutron stars which are several times more massive than the Tolman-Doobry-Wotsit limit. As I say, I'm getting more data on stellar remnants and low mass giants so the plot is already out of date, so this is yet another work in progress.

 

[Ziljan]

I. I think the issue with the unsmooth range of B remnant Neutron Stars has to do with a few key factors.

1. 
   [*=1] As they evolve off of the main sequence, the more massive stars lose quite a bit of mass (~30%).
   [*=1]Your factor for the total initial mass loss for neutron stars is a bit high. It should be closer to ~1/8. For instance the theoretical mass limits for a ZAMS-> NS is 8-25 solar masses. Where as the mass limits for a NS are 1.1 to 3 solar masses. That works out to 1/8 mass remnants.
   [*=1]B stars come in waves and live short lives. This makes finding their evolved counter parts quite challenging. The data is bound to be a bit spotty unless you take a sweep over several disparate random (nebula, and non nebulae) sectors in the spiral arms where star formation in a periodically recurring event. Too much sampling near the core or within nebulae will bias the results towards the young and old extremes. However, outside of these areas, B stars (and their evolved remnants) are pretty darn rare.

If you combine these factors, then your stellar remnant curve would be much smoother. Likewise, the "gap" between the MS and the remnants will also be represented as a continuous region whose width is due to the time it takes a star to actually evolve off of the main sequence.​

II. The issue with the "missing" evolved "B" stars is probably because of the way you presented the data as Age vs Mass, instead of Temp vs Luminosity. Lower mass B stars only lose between 1-10% of their mass as they evolve off the main sequence. So they tend to bunch up with over lapped with the evolved higher mass "B" stars if you just look at the Age and the Mass. This is partly why the HR diagram was invented. To the show the separation of the main groups and also to show the path they take as they evolve. It's also because we can't measure the age or the mass directly from earth. Only indirectly via modeling and iterative calculations. Try remodeling with an HR diagram and the expected population groups will probably jump out quite nicely.

 

[The Tick]

+1 rep to you ALL, just for having such a mindblowing discussion on a gaming forum!You guys lost me a long time ago. And that's coming from a science PhD.That's why I love this community ;-)

 

[Andrew Gaspurr]

Are there also indications about the denominations of protostars available? The reason I ask is, I read an article on star cluster formation within a given cloud and the theory that those clouds contracted at different speeds, depending on their mass. It was related to the HR diagram, specifically to the time frame in which protostars enter the main sequence. It was postulated that the bigger the cloud, the faster the rate of star formation and one argument for it was, that in bigger clouds protostars jump to main sequence much more rapid and hence theiir appearance on the HR diagram would be faster than generally anticipated.

... or something like that.

Does the FDev Stellar Forge also use a letter code for Herbigs and Tauris (and maybe even ZAMS)?

 

[Jackie Silver]

Does the FDev Stellar Forge also use a letter code for Herbigs and Tauris (and maybe even ZAMS)?

As far as I can see the T Tauris use a variety of luminosity codes and temperature subdivisions, but without specifying to which spectral class those subdivisions belong - so a TTS7 VA might refer to one with a temperature between 2340K and 2510K (equivalent to an M7 VA) or it might refer to one with a temperature between 4000K and 4150K (equivalent to a K7 VA); there's no indication which is which until you scan it and find the temperature, although when the luminosity class is higher (VAB, VB) you have a good indication that the T Tauri is probably G or F temperature. I believe the cutoff between TTS and He Ae/Be is 3 solar masses in game but I'm not sure.

Exactly how (if) the T Tauris progress along the Hayashi / Henyey tracks (as Ziljan mentioned earlier) is something that bears looking at. Also the relationship between TTS / He Ae/Be and VZ luminosity class - stars with a luminosity class of VZ tend to be hotter than the maximum that their spectrum should be, which doesn't make sense to me. VZ seems to be strongly associated with young and bright, so it may be the next step after TTS: TTS -> VZ -> (VI, VA, VAB, VB, whatever); I'm hoping we'll get proper stellar evolution tracks for stars in the Forge.

I messed up when I added the data from other surveys into my log and accidentally included a bunch of duplicates and unreliable data. I'm trying to clean it up now.

For reference (and despite what the stellar descriptions say) the spectral class boundaries are, so far as I know:

Y < 700
700 < T < 1300
1300 < L < 2000
2000 < M < 3700
3700 < K < 5200
5200 < G < 6000
6000 < F < 7500
7500 < A < 10000

With each split into ten equal subdivisions from 9 (coldest) to 0 (hottest). I'm not sure what the B upper and O lower boundary are, can work it out later if it's important.
These work for everything except VZ.

 

[Pirin]

It looks as if I've been chasing phantoms - I had a good look at some old data we collected on around 3000 planets and there were no HMC worlds with surface temperature above 1000K and no atmosphere. There's HMC above 1000K with an atmosphere, and MRW above 1000K with or without an atmosphere.

Jackie, i have something for you

Spoiler

 

[Ziljan]

VZ seems to be strongly associated with young and bright, so it may be the next step after TTS: TTS -> VZ -> (VI, VA, VAB, VB, whatever); I'm hoping we'll get proper stellar evolution tracks for stars in the Forge.

VZ is thought to describe young near ZAMS stars, so you are right that they are likely the next step after TT or HABe.

The temperature changes though vary depending on mass. For lower mass stars, the temperature increases with age, up to a point. However for higher mass stars (~1.5 solar masses), the temperature seems to decrease from birth. The "brightness" (which is a synonym for Luminosity) is also dependent on the radius which generally increases with age, and it dominates the stefan-boltzmann equation even with the temperature decrease in larger stars. So younger stars are dimmer than more mature stars. Now we know the MK designations for the luminosity rankingshould be VA > VAB > VB > VZ. Meanwhile the temperature ranking might be VAB > VA ~ VB > VZ for low mass stars, and VZ > VB > VAB > VA for higher mass stars. Meanwhile the radius might go as VA > VAB > VB > VZ. This is theoretical though. I would be very curious to know which model the stellar forge uses for temperature and luminosity evolution at various masses. And also whether it takes into account mass loss rates from aging.

 

[Jackie Silver]

Brilliant, thanks Pirin. By good fortune I'm in EESHORKS right now, only 300ly away.

@Ziljan - I'd say tentatively that the forge does take mass loss with age into account from a look at the Kn IIAB orange giant data there's a correlation with mass decreasing with age. I'll look at it further. Have you seen VZ used elsewhere, then? I hadn't seen Z being used for anything other than metallicity, or seen the A / AB / B classifications used anywhere other than supergiants, so my first guesses were that VZ was an indicator of low metallicity stars - obvs. that turns out not to be the case.

 

[Ziljan]

@Ziljan - I'd say tentatively that the forge does take mass loss with age into account from a look at the Kn IIAB orange giant data there's a correlation with mass decreasing with age. I'll look at it further. Have you seen VZ used elsewhere, then? I hadn't seen Z being used for anything other than metallicity, or seen the A / AB / B classifications used anywhere other than supergiants, so my first guesses were that VZ was an indicator of low metallicity stars - obvs. that turns out not to be the case.

I meant mass loss rates on the main sequence, eg from radiation, instability, flares, coronal mass ejections, pulsing etc.

In science, we quickly run out of letters, so they have to do double duty, and it's all about the context. That is why so many greek symbols and bars and dots get used, lol. a, ab, b can also be used to name or describe specific elements in binary pairs, and maybe that is what you were seeing? As for the A / AB / B / Z classifications in this case, the following familiar diagram may be useful, and btw, when they say "V dwarfs" , they are referring to normal MS stars, not actual white/red/brown dwarfs:




My logs are pretty empty compared to your vast in game experience, Jackie. So I have only seen VZ stars when I wasn't logging them! But now that I am looking for younger more metal rich stars, I can't seem to find them.